1. Field of the Invention
The present invention relates to a reciprocatory piston type multi-cylinder refrigerant compressor for a refrigeration system accommodated in an automobile, and more particularly, it relates to a reciprocatory piston type compressor provided with an improved internal construction thereof capable of preventing pressure loss before delivery of the compressed refrigerant gas and of suppressing vibration and noise.
2. Description of the Related Art
Reciprocatory piston type refrigerant compressors such as a wobble plate operated reciprocatory piston type variable displacement compressor, and a swash plate operated reciprocatory piston type fixed displacement compressor are conventionally used for compressing a refrigerant circulating through a refrigeration system of e.g., an automobile air conditioner.
U.S. Pat. No. 4,732,545 assigned to the same Assignee as the present patent application discloses a typical wobble plate type compressor.
FIGS. 23 and 24 illustrate a conventional wobble plate type variable displacement refrigerant compressor similar to the compressor disclosed in the above-mentioned U.S. Pat. No. 4,732,545. In FIGS. 23 and 24, the wobble plate type compressor is provided with an axial cylinder block 90 having a-plurality of cylinder bores 91 arranged around and parallel to a central axis of the cylinder block 90, and a plurality of single headed pistons 92 reciprocated in the respective cylinder bores 91 to compress the refrigerant in the form of a gas. The compressor having single headed pistons 92 is also provided with a front housing 94 attached by bolts 90a to one of the axial ends, i.e., a front end of the cylinder block 90 to define a crank chamber 93 therein, and a rear housing 98 attached by the same bolts 90a to the other end, i.e., a rear end of the cylinder block 90 via a suction valve sheet 95, a valve plate 96, and a discharge valve sheet 97 to define an outer suction chamber 87 and a discharge chamber 88. The suction and discharge valve sheets 95 and 97 are formed with a plurality of flapper type suction and discharge valves 95a and 97a therein, respectively. The movement of the flapper type discharge valves 97a of the discharge valve sheet 97 from the closed position thereof to the open position is limited by a retainer element 89 disposed in the discharge chamber 88.
An axial drive shaft 80 is arranged in the crank chamber 93 of the front housing 94 to extend coaxially with a central axis of the cylinder block 90. The drive shaft 80 has one end thereof, i.e., a front end extending outwardly beyond the frontmost end of the front housing 94 via a shaft seal 99a and a front rotary bearing 99b, and the other end thereof supported by a rear rotary bearing 99c seated in a central bore 90b of the cylinder block 90. Thus, the axial drive shaft 80 is rotatable in the crank, chamber 93.
A rotor 81 is fixed to a part of the drive shaft 80 so as to be rotated together with the drive shaft 80, and axially supported by a thrust bearing 81a seated on the inner face of the front housing 94. A sleeve element 82 is slidably mounted on the drive shaft 80, and axially and frontwardly pressed by a spring element (not illustrated in FIG. 1). The rotor 81 is formed with an elongated through-hole 81b in which a pin 83a is movably engaged connecting the rotor 81 to a swash plate 83 that is pivotally supported by the sleeve element 82 via a pair of lateral trunnion pins 82a. The swash plate 83 pivoting about the trunnion pins 82a so as to assume a variably inclined position thereof with respect to a plane vertical to the axis of the drive shaft 80 is rotatable with the drive shaft 80.
A non-rotatable wobble plate 85 is supported on the swash plate 83 via a thrust bearing 84a and a cylindrical slide bearing 10, and is provided with a radially outermost portion 85a thereof engaged with one of the bolts 90a thereby preventing same from being rotated together with the swash plate 83. Thus, only a pivotal motion of the swash plate 83, thereby changing the angle of inclination thereof about the trunnion pins 82a, is transmitted to the wobble plate 85.
The wobble plate 85 has a rear end face having sockets formed therein for movably receiving one ball-end of each of a plurality of connecting rods 86 connected, via the other ball-ends thereof, to the afore-mentioned pistons 92. Therefore, when the drive shaft 80 is rotated by an outer drive power source, such as a vehicle engine, the swash plate 83 is rotated together to cause a wobbling motion of the non-rotatable wobble plate 85, thereby reciprocating the pistons 92 in the respective axial cylinder bores 91 of the cylinder block 90. The volume of respective cylinder bores 91 is changed by the reciprocation of the pistons 92 from the top to bottom dead centers thereof and vice versa in the corresponding cylinder bores 91. Therefore, the refrigerant gas is drawn from the suction chamber 87 of the rear housing 98 into the respective cylinder bores 91 to be compressed by the reciprocated pistons 92 in the cylinder bores 91, and is discharged toward the discharge chamber 88 of the rear housing 90.
As is clearly shown in FIG. 23, the suction chamber 87 of the rear housing 98 has an annular form, and is arranged radially outside the discharge chamber 88 via a partition wall. The outer suction chamber 87 is provided with a suction inlet 87a for introduction of the refrigerant gas from the external refrigerating circuit of a vehicle refrigerating system, and the discharge chamber 88 is provided with a delivery outlet 88a for delivery of the compressed refrigerant gas toward the external refrigerating circuit.
A plurality of suction ports 96a (in most cases, the number is equal to that of the cylinder bores 91) are formed in the outer peripheral portion of the valve plate 96 and the discharge valve sheet 97 in such an arrangement that the respective suction ports 96a are substantially axial in alignment with the respective cylinder bores 91. The suction ports 96a provide a fluid communication between the suction chamber 87 and the respective cylinder bores 91 during the suction stroke of the reciprocatory pistons 92 in the respective cylinder bores 91 from the top dead center to the bottom dead center, thereby enabling the refrigerant gas before compression to be drawn from the suction chamber 87 into the volume-increasing cylinder bores 91 through the flapper type suction valves 95a of the suction valve sheet 95 elastically moved to their opening positions.
Similarly, a plurality of discharge ports 96b (the number is equal to the number of cylinder bores 91) are formed in the radially internal portion of the suction valve sheet 95 and the valve plate 96 in such an arrangement that the respective discharge ports 96b are substantially axial in alignment with the respective cylinder bores 91. The respective discharge ports 96b provide a fluid communication between the respective cylinder bores 91 and the discharge chamber 88 during the discharge stroke of the respective reciprocatory pistons 92 from the bottom dead center to the top dead center, thereby enabling the compressed refrigerant gas to be discharged from the volume-decreasing cylinder bores 91 toward the discharge chamber 88 through the flapper type discharge valves 97a of the discharge valve sheet 97 elastically moved to their opening positions limited by the retainer 89.
Nevertheless, with the conventional wobble plate type variable displacement refrigerant compressor of FIGS. 23 and 24, it should be noted that each of the suction and discharge valves 95 and 97 in the flapper form is made of a thin elastic plate material so that the valve is constantly elastically urged toward the closing position thereof. Therefore, the flapper valve must always be moved from the closing to opening position thereof against the elastic force exerted by the valve per se, and accordingly, a delay in the suction of the refrigerant gas and a delay in the discharge of the compressed refrigerant gas occur, and as a result, a considerable amount of refrigerant pressure loss occurs, thereby lowering the volumetric efficiency of the compressor. The pressure loss becomes great either when a high load is applied to the compressor or when the compressor is operated at a high speed.
Further, when the suction or discharge valve in the flapper form returns to the closing position thereof, it strikes against the end face of the valve plate and produces a loud noise, and may additionally be damaged or broken.
Moreover, the above-mentioned delay in the suction of the refrigerant gas before compression into the cylinder bores will cause the gas to make contact with the partition wall between the suction and discharge chambers 87 and 88 in the course of the gas flowing from the suction inlet 87a to the cylinder bores 91. Therefore, the refrigerant gas before compression is exposed to heat transmitted from the high temperature discharge chamber 88 via the partition wall and accordingly, the refrigerant gas before compression is thermally expanded prior to entering the cylinder bores 91. The thermally expanded refrigerant gas thus cannot be sufficiently compressed by the reciprocatory pistons 92 within the cylinder bores 91, and therefore an adverse affect is imparted to the compressing performance of the compressor.